Ch. 13, Development Flashcards
three perspectives on brain development
- structural brain developmnet = predicts behavior
- Behavior = predicts structural brain development
- Other factors are more important: SES, hormones,etc which can all influence brain developmnent
Major findings from research on brain development and SES
Noble 2015 =
1. Lower family income = decreased cortical surface area across frontal, temporal and parietal lobes
2. Worse cognitive perfrormance across language and memory domains
Tower of hanoi, what it tests, profiency ages
tests planning = tests frontal lobe development
age 10: can do very simple forms of this task
age 15-17 can do much more complex versions of the task
Preformation idea in the 1800s
scientists used to believe that sperm and egg cells had tiny humans that just grew up in the womb
reality: embryos look nothing likle adults they become
What supports Darwin’s idea of common ancestry?
that embryos of diff species more closely resemble each other than their parents= supports darwin’s view
Period of zygote, em,bryo, and fetus
Zygote: conception to 2 weeks
embryo: 2 weeks-8 weeks
fetus: 9 weeks–birth
what is the three chambered brain and when is it visibnle in humans?
visible at day 28
includes forebrain, midbrain, hindbrain
Fetal terms for the forebrain, midbrain, and hindbrain
Prosencephalon = will become forebrain
Mesencephalon= will become midbrain
Thombencephalon = will become hindbrain
Mesencephalon + thombencephalon = brainstem
Formation of the neural tube process
- Outermost layer of the embryonic disk becomes thicker
- Forms the neural plate: primitive neural tissue that develops
- = forms the neural tube, a structure in early development from which the brain and spinal cord arise; nursery of cells for the entire CNS
What day is the neural tube developed and what happens if it is defective?
24 days
neural tube = nursery of cells for the entire CNS
if it doesn’t close fully = spinal cord defects
Teratogens and timing
earlier the terotogen = worse timing
“Safest” time to have terotagen: between 6-8 weeks, because migration of the cells hasnt occured yet but b
Anterior vs posterior part of the neural tube
anterior= beomes the spinal cord
posterior = becomes the brain
3 stages of prenatal brain development
- C ell birth (includes neurogenesius and glialgensis)
- Neural migratioin: cells move to specific brain locations
- Differentiation: have to form particular type of cell
4 stages of brain development that occur AFTER BIRTH
- Neural maturation (growth of dendrite and axons)
5., Synaptogensis/forming synapses - Synpatic pruning
- Myelogenosis (formation of myelin) up until age 25-30
ESCs
embryonic stem cells: can become any cell in the embroyo/most unspecialized type
Requirements for a cell to be a stem cell
- Must be able to reproduce itself indefinetly
- Differentiate into more than ONE type of specialized cell
symmetrical vs asymmetrical division of stem cells
symmetrical: one stem cell – produces two stem cells
asymmetrical: one stem cell – produces one stem cell and onew other type of precurser/progenitor cell – which then divides into further cells
4 types of stem cells from most general to most specific
- Totipotent: omnipotent, do everything, most unspecialized, can give rise to embyronic cells and placenta cells, INCLUDES ZYGOTE AND CELLS OF FIRST 2 DIVISIONS
- Pluripotent: can differentiate into all embryonic cells, BUT NOT placenta cells (embryonic stem cells, ESCS)
- Multipotent: can differentiate into multiple specialized cell types found in specific tissues/organs (neural stem cells) but still MULTIPLE TYPES OF CELLS
- Unipotent: single lineage, example: spermatogonial stem cells, can reproduce indefinetly but only as sperm cells
PUMT
Progenitor cell/percursor cell/ neuroblast/glioblast
progenitor/precursor: cell derives from a stem cell that migrates and produced a neuron or glial cell
neuroblast: product of the progenitor cell = then gives rise to diff types of neurons
glioblast: product of a progenitor cell = gives rise to diff types of glial cells
start of neurogensis, differentiation, migration
Neurogenesis 6-25 wks
Migration and Differentiation: 8 - 29 weeks.
Maturation (green bar/green numbers). 20 wks - after birth
Paternal FASD
pre-conception drinking of the father can create FASD = sperm are continously developing and can get harmed in this process
radial glia
type of neural stem cell (NSC) self renews, produces all different types of neurons
subventricular zone in fetal brain
contains a lining of all NSCs: contains map of cortex to be able to direct neurons to where they should go in the brain
4 steps of cell differentiation
- Uncomitted precursor (like a NSC)
- Cells with some segregation of determinants (progenitor)
- further segregation of determinations
- influenced by intercellular environmernt
= diverse cells
two types of signals that specify cell fate
intrinsic: inherited from mother cell
extrinsic: chemical cues from cell’s surroundings
function of radial glial cells in migration
- Radial glia have 2 general functions. They are neural stem cells
- They also act like a path-finding scaffold, allowing the migrating neuroblasts (their daughter cells) to migrate from the ventricular surface, all the way up to the cortical surface. The immature neurons “climb” up the radial glia cells as they are migrating.
difference between stem cells and progenitor cells
progenitor cells can only divide a limited number of times, not indefinitely
progenitor cells can only divide into their target cells, much more specialized than stem cells
Two types of neural maturation and their rates (stage 4)
- dendritic growth: OCCURS MUCH SLOWER, rate of microns/per day, provide surface area for synapses with other cells
Arborization= slow growth - Axonal extension: VERY FAST, mm/per day, presynaptic guide the development of postsynaptic terminals, extend toi targets in order to intitiate synapse formation 1000 times faster than dendritic growth
-MAJORITY OF MATURATION HAPPENS AFTER BIRTH BUT BEGINS AT 20 WEEKS PRENATALLY
ASD symptoms, rate, gender difference
- impaired social interaction
- restricted range of interests
- robotic tone/abnormal communication skills
- repetitive movements
1/54 children
more severe and 4x more prevalen t in boys: no reason known as to why
Neural causes of ASD
neuronal maturation that occurs TOO FASt = too much brain volume in the F-A-T: frontal, amygdala, and temporal lobes, as well as cerebellum (responsible for social and motor correction)
girls vs boys in ASD brain volume
girls, age 7: TD and ASD children gray matter volumes are equal
boys: age 13, gray matter volumes betwqeen TD AND ASD have still not equaled out
Santiago Cajal and growth cones
proposed the idea of growth cones: guide the growth of axons
Filopedia vs lamellipodium
filopedium/pedia: finger-like projections, constantly growing/retracting: sensory structures looking for guidance molecules = TELL THEM WHERE TO GROW = IN ORDER TO SYNAPSE WITH OTHER NEURONS SUCCESSFULLY (SYNAPSE)
lamellipodium: flat extensions, motile structure that allows growth cone to move through its environment (MOVE)
CAMS
cell adhesion molecules
cue for growth cones
“cellular glue”: allow cone to physically grab onto the environment “stick to it” and move to its target, manufactured by other cells
troPIC molecules
chemoattractants or chemorepulsants: either attract or repel pathfinding axons
secreted and are diffusable
difference between tropic and trophic
tropic: means movement
trophic: refers to nutrition
synaptogensis prenatally vs after birth
month 5: first synaptic contacts made
month 7: more synaptic development of deepest cortical neurons
MOST OCCURS AFTER BIRTH:
how doies the brain/cortex mature?
developed/matures from bottom up
Chisels
anything that facilitates synaptogenesis: genetic signals, experience, hormones, even SES
Why does the cortex become thinner with age (usually up to 20) and what pattern does this occur in?
becomes thinner bc
1. synaptogensis
2. expansion of white matter presses on the cortex, “forces it” to be thinner
cortical thinning occurs from back to front, just like in developmnent: caudal to rostral pattern
at what two points does synaptic pruning peak?
toddlers; adolescence: why these are very drastic behavior change times
Neural darwinism and neurotrophic factors
cell death occurs like natural selection: neurons must compete for neurotrophic factors (nutritional components that keep it alive) and it is survival of the fittest
What secretes neurotrophic factors and what part of the cell receives them?
post-synpatic targets secrete neuotrophic factors, PRESYNPATIC recieve them
apoptosis vs necrosis
apoptosis: controlled, healthy cell death/recylcing
necrosis: uncontrolled, damaging cell death, explosive, unplanned
what do radial glia become once neural migration is complete?
astrocytes
oligodendrocytes
produce myelin in the CNS
Myelination and maturation
used as an index for cerebral maturation
myelination (stage 7) and order that structures are myelinated in
first occurs at 20 weeks, but majority occurs just after birth
Last myelinating areas= areas that control the highest function (like the PFC)
earliest myelinating: control simple movements
sex differences in total volume, gray matter volume, white matter volume
total volume: males larger bc larger bodies
gray matter: women peak sooner than men
white matter volume: no sex differences in timing, men still have more due to body size
What causes decrease in gray matter?
synaptic pruning/ apoptosis
what increases white matter?
myelin development
